APPENDIX 



459 



bach's Flora of the British West Indian Islands (1864). Yet, as 

 pointed out by Sagot, when writing in the Bulletin de la Societe 

 Botanique de France in 1875 (XXII., 292), the seed was very accu- 

 rately described by Jacquin in his work on American plants in the 

 middle of the eighteenth century. It was also described and figured 

 by Bentham a hundred years after in the Flora Brasiliensis of 

 Martius (Vol. XV., part 1, p. 169, tab. 46, 1859-62). Both these 

 works are quoted by Grisebach in connection with the plant, and his 

 lack of reference to the seed seems unaccountable. Perhaps the 

 reason may lie in the same doubt that first suggested itself to Sagot ; 

 that is to say, whether two plants, like M. mens and M. pruriens, 

 that are associated in the same genus by their floral characters, 

 would possess seeds so different. Grisebach, with Jacquin' s and 

 Bentham' s volumes by his side, says nothing of the seed of either 

 species. 



The difference in appearance between the large, globoid, iron-grey 

 seeds of Mucuna urens and the small, sub-reniform, mottled brown, 

 shining seeds of M. pruriens is well brought out in Bentham' s figures. 

 The first are thick-shelled, an inch across, and nearly surrounded by 

 the black raphe. The second, which the present writer compares 

 with ordinary Phaseolus seeds and Sagot with small haricots, are 

 relatively thin-shelled, barely half an inch in length, and possess a 

 large scar but no circular raphe. The seeds of M. urens, again, 

 possess great buoyancy. Those of M. pruriens, as my experiments 

 indicate, possess none. The first are distributed unharmed by the 

 ocean currents. The second have evidently been dispersed by man 

 along trade routes. The first are characteristic of beach-drift in the 

 West Indies and elsewhere. The second have never been recorded 

 from beach-drift, nor are they at all likely to occur there. 



For a long while I clung to the use of the name of Mucuna pruriens 

 as applied to a species with seeds of the M. urens type, since its 

 employment was backed by high authorities. However, when I 

 included seeds of this type under the name in a collection of West 

 Indian drift sent to the Natural History Museum in 1912, Dr. Rendle 

 kindly pointed out that they were not those of M. pruriens, which 

 were much smaller and more oblong in form, and that they were 

 probably those of M. urens. This decided the matter. In the 

 treatment of the drift seeds of Mucuna in other parts of this work 

 it is pointed out that there are two kinds of seeds of the urens type 

 dispersed by currents; and the specific name of " pruriens " was in 

 the above-named collection applied by me to the seeds which are 

 now designated in these pages as 44 near urens," seeds that may be 

 those of M. altissima, DC, a matter discussed on p. 120. 



Note 11 (p. 60). 



The relation between the floras of Ascension and St. Helena and the 



currents. 



As we learn from Hemsley (Chall. Bot., III., 32-4), we have no 

 positive proof that more than two of the flowering plants of Ascen- 



